A warning about Keydata, the bust investment company at the centre of a £105m black hole, was given to the Financial Services Authority by the chairman of accountancy firm KPMG four years ago.

Guardian Money has also seen an email stating HSBC complained about "misleading and inaccurate information" in Keydata marketing material at around the same time, autumn 2005.

The documents could strengthen the case for compensation for thousands of savers whose money was lost when Keydata went into administration in June.

Both focus on the brochure and application form for Keydata's Secure Income Bond Issue 1, distributed in summer 2005, mostly to independent financial advisers who sold the bond to clients in return for 3% initial commission and an annual 0.5% thereafter.

The Secure Income Bond promised an annual 7.5% return, based on an obscure US investment known as life settlement bonds – effectively life insurance plans given up by their holders. The bonds benefited when the former policyholders died prematurely.

In its sales brochure, Keydata said: "KPMG – one of the big four accountancy firms – constructed the financial models used to structure the bond. It also checks the credit ratings of the insurance companies issuing the contracts and monitors the credit rating of the portfolio of investments." None of this was true. Although KPMG had done some internal research into life settlements as an investment concept, it did not construct the Keydata financial models, or have any involvement in checking credit ratings.

KPMG did not see the statement for Issue 1. But when Issue 2 was launched in October 2005 with the same wording, KPMG objected "most strongly" to Keydata. A letter sent this month by John Griffith-Jones, UK chairman of KPMG, to a member of the Keydata victims action group (keydatavictims.ning.com), says: "We dissociated ourselves from the brochure and called upon them [Keydata] to bring that to the attention of all recipients of the brochure."

Keydata failed to respond. KPMG then made a complaint to the FSA, but the watchdog did not move formally against Keydata.

HSBC also dissociated itself from Keydata's brochure, which said: "Trading of the insurance contracts is overseen by HSBC." HSBC Bank USA says: "We have had no relationship with Keydata with respect to Secure Income Bonds."

An FSA spokesperson said: "The FSA is unable to comment on Keydata to prevent prejudice to legal actions which are currently progressing."

The FSCS added: "The FSCS is now at an advanced stage of its investigations and analysis into issues arising out of the administration of Keydata, with a view to confirming its involvement in compensating investors with claims against the firm."